Drought Resistance Traits Research Articles

Sequence-Structure Comparative and Network-Based Prediction of Drought Gene Candidate Regulator in <i>Elaeis guineensis</i>

Drought poses a significant threat to global food security, particularly impacting crops like oil palm. Selecting genes for genome editing to enhance drought tolerance presents formidable challenges. To ensure that the target gene is chosen correctly and results in the desired character, a pilot study is necessary to determine the target gene for knockout. Two genes drought-related, AtBRL3 and AtOST2, were scrutinized in this context. Aligned with the Elaeis guineensis genome, their neighbouring proteins and gene ontology were analysed to identify potential targets for genome editing. AtBRL3, identified as BRL1 (XP_010913986.1) in E. guineensis, exhibited 58.48% identity and 100% coverage. It interacts with 12 nodes, including BIR1, BRI1, and AT2G20050, crucial for signalling pathways and cellular responses. Molecular function analysis revealed kinase activity. AtOST2 showed high similarity to plasma membrane ATPase/HA1 (XP_010913679.1) in E. guineensis, with 87.46% identity and 100% query cover. It correlated with 14 genes associated with ABA stimulus, stomatal movement, and hormone response. EgBRL1 and EgHA1, resembling AtBRL3 and AtOST2, respectively, emerge as promising targets for developing drought-tolerant oil palm cultivars through gene editing. Nonetheless, further validation through in vitro gRNA target selection and in vivo conversion of OST2/BRL3-containing plasmids in oil palm calluses is indispensable to demonstrate their efficacy in conferring novel drought resistance traits.

Annual-perennial lifespan variation in Chaenactis douglasii suggests a drought escape strategy in warm-arid environments.

Intraspecific variation in drought resistance traits, such as drought escape, appear to be frequent within wild, ruderal forb species. Understanding how these traits are arrayed across the landscape, particularly in association with climate, is critical to developing forbs for wildland restoration programs. Use of forbs is requisite for maintaining biological diversity and ecological services. Using 6074 greenhouse-grown Chaenactis douglasii seedlings from 95 wild, seed-sourced populations across the western United States, we recorded bolting phenology and estimated genome size using flow cytometry. Mixed-effects regression models were used to assess whether climate of seed origin was predictive for bolting phenology and genome size. Variation in bolting, reflecting an annual vs. perennial lifespan in this species, was observed in 8.7% of the plants, with bolting plants disproportionately occurring in locations with warm, arid climates. Populations with increasing heat and aridity were positively correlated with observed bolting (r = 0.61, p < 0.0001). About one-third (22%) of the total (61%) lifespan variation was attributed to seed source climate and annual heat moisture index, a measure of aridity. Genome size had no significant effect on bolting. Projected climate modeling for mid-century (2041-2070) supports an increasing occurrence of annual lifespan. Our analyses support a drought escape, bet-hedging strategy in C. douglasii. Populations exposed to greater aridity exhibited a higher proportion of individuals with an annual lifespan. Drought escape leading to an annual lifespan can affect how seeds are propagated and deployed for climate-informed restoration.

Linking physiological drought resistance traits to growth and mortality of three northeastern tree species.

Climate change is raising concerns about how forests will respond to extreme droughts, heat waves and their co-occurrence. In this greenhouse study, we tested how carbon and water relations relate to seedling growth and mortality of northeastern US trees during and after extreme drought, warming, and combined drought and warming. We compared the response of our focal species red spruce (Picea rubens Sarg.) with a common associate (paper birch, Betula papyrifera Marsh.) and a species expected to increase abundance in this region with climate change (northern red oak, Quercus rubra L.). We tracked growth and mortality, photosynthesis and water use of 216 seedlings of these species through a treatment and a recovery year. Each red spruce seedling was planted in containers either alone or with another seedling to simulate potential competition, and the seedlings were exposed to combinations of drought (irrigated, 15-d 'short' or 30-d 'long') and temperature (ambient or 16days at +3.5°C daily maximum) treatments. We found dominant effects of the drought reducing photosynthesis, midday water potential, and growth of spruce and birch, but that oak showed considerable resistance to drought stress. The effects of planting seedlings together were moderate and likely due to competition for limited water. Despite high temperatures reducing photosynthesis for all species, the warming imposed in this study minorly impacted growth only for oak in the recovery year. Overall, we found that the diverse water-use strategies employed by the species in our study related to their growth and recovery following drought stress. This study provides physiological evidence to support the prediction that native species to this region like red spruce and paper birch are susceptible to future climate extremes that may favor other species like northern red oak, leading to potential impacts on tree community dynamics under climate change.

A phenotypic integration approach to breeding seedlings for early vigor and drought resistant traits

Silphium is being domesticated as a new perennial biomass and oilseed crop. As a consequence of selection to improve yield, seedling´s growth and survival are expected to be affected indirectly. The phenotypic integration theory predicts that selection acts on the correlation structure among root and leaf traits. In order to assess the possibility of breeding simultaneously for early vigor and drought tolerance in Silphium integrifolium, two goals were proposed: 1) to assess trait coordination within and between plant modules in improved and wild accessions, and 2) to evaluate the effectiveness of leaf traits as selection criteria to develop vigorous and drought tolerant seedlings. Improved accessions were selected using three criteria: 1) seed yield (SEED); 2) leaf traits related to fast growth (FAST) or 3) slow growth (SLOW). FAST and SEED accessions accumulated biomass faster and had higher leaf area-root length ratio, than SLOW and wild. FAST´s traits were related to early aboveground vigor such as thinner leaves and higher specific leaf area, but roots were more superficial and their volume smaller, which is linked to low vigor and soil exploration. This has consequences for early outperformance of weeds and soil evaporation reduction, but may also imply tradeoffs, diminishing resistance to drought. We conclude that leaf traits cannot be used to select for vigorous and drought resistant seedlings, because the lack of coordination between leaves and roots. Nonetheless, phenotypic integration suggests that leaf traits can be used to select Silphium varieties for different target environments.

Lethal combination for seedlings: extreme heat drives mortality of drought-exposed high-elevation pine seedlings.

Hotter drought- and biotically-driven tree mortality are expected to increase with climate change in much of the western United States, and species persistence will depend upon ongoing establishment under novel conditions or migration to track ecological niche requirements. High-elevation tree species may be particularly vulnerable to increasing water stress as snowpack declines, increasing the potential for adult mortality and simultaneous regeneration failures. Seedling survival will be determined by ecophysiological limitations in response to changing water availability and temperature. We exposed seedlings from populations of Pinus longaeva, Pinus flexilis, and Pinus albicaulis to severe drought and concurrent temperature stress in common gardens testing timing of drought onset under two different temperature regimes. We monitored seedling functional traits, physiological function, and survival. The combined stressors of water limitation and extreme heat led to conservative water use strategies and declines in physiological function, with these joint stressors ultimately exceeding species' tolerances and leading to complete episodic mortality across all species. Growing conditions were the primary determinant of seedling trait expression, with seedlings exhibiting more drought-resistant traits such as lower specific leaf area in the hottest, driest treatment conditions. Water stress-induced stomatal closure was also widely apparent. Under adequate soil moisture, seedlings endured prolonged exposure to high air and surface temperatures, suggesting broad margins for survival. The critical interaction between soil moisture and temperature suggests that rising temperatures will exacerbate growing season moisture stress. Our results highlight the importance of local conditions over population- and species-level influences in shaping strategies for stress tolerance and resistance to desiccation at this early life stage. By quantifying some of the physiological consequences of drought and heat that lead to seedling mortality, we can better understand the future effects of global change on the composition and distribution of high-elevation conifer forests.

Root traits and biomass production of drought‐resistant and drought‐sensitive arabica coffee varieties growing under contrasting watering regimes

AbstractDrought is a major factor affecting coffee production, and different genotypes exhibit varying degrees of resistance to drought stress. We examined root traits and biomasses of drought‐resistant (74110, Angafa, Bultum, Chala, and Gawe) and drought‐sensitive (75227, Koti, Melko CH2, Menasibu, and Mokah) Coffea arabica varieties at seedling stage under contrasting watering regimes (water stressed and well watered) for 30 days followed by 15 days of recovery to identify the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of arabica coffee varieties. We used a split‐plot design with three blocks, where watering regime was the whole‐plot factor and variety was the subplot factor. During water‐stress and recovery periods, the interaction effect between watering regime and variety significantly affected root traits and dry matter partitioning, while the watering‐regime main effect affected biomass. We observed a higher (1) tap root diameter (0.34 cm), lateral root number (80.7), and root volume (4.7 cm−3) for 74110; (2) lateral root number (79.3), specific root length (24.8 cm g−1), and root‐mass ratio (0.41 g g−1) for Bultum; and (3) root length density (3.3–5.2 cm cm−3), root angle (42.6°–47.8°), root‐mass ratio (0.40–0.42 g g−1), and root‐shoot ratio (0.67–0.72 g g−1) for Angafa, Chala, and Gawe under water‐stressed condition. During both study periods, biomasses were much lower under water‐stressed than under well‐watered condition. The findings show the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of young arabica coffee.

Comparative analysis and characterization of the chloroplast genome of Krascheninnikovia ceratoides (Amarathaceae): a xerophytic semi-shrub exhibiting drought resistance and high-quality traits

BackgroundKrascheninnikovia ceratoides, a perennial halophytic semi-shrub belonging to the genus Krascheninnikovia (Amarathaceae), possesses noteworthy ecological, nutritional, and economic relevance. This species is primarily distributed across arid, semi-arid, and saline-alkaline regions of the Eurasian continent, encompassing Inner Mongolia, Xinjiang, Qinghai, Gansu, Ningxia, and Tibet.ResultsWe reported the comprehensive chloroplast (cp) genome of K. ceratoides, characterized by a circular conformation spanning 151,968 bp with a GC content of 36.60%. The cp genome encompassed a large single copy (LSC, 84,029 bp), a small single copy (SSC, 19,043 bp), and a pair of inverted repeats (IRs) regions (24,448 bp each). This genome harbored 128 genes and encompassed 150 simple sequence repeats (SSRs). Through comparative analyses involving cp genomes from other Cyclolobeae (Amarathaceae) taxa, we observed that the K. ceratoides cp genome exhibited high conservation, with minor divergence events in protein-coding genes (PCGs) accD, matK, ndhF, ndhK, ycf1, and ycf2. Phylogenetic reconstructions delineated K. ceratoides as the sister taxon to Atriplex, Chenopodium, Dysphania, and Suaeda, thus constituting a robust clade. Intriguingly, nucleotide substitution ratios (Ka/Ks) between K. ceratoides and Dysphania species for ycf1 and ycf2 genes surpassed 1.0, indicating the presence of positive selection pressure on these loci.ConclusionsThe findings of this study augment the genomic repository for the Amarathaceae family and furnish crucial molecular instruments for subsequent investigations into the ecological adaptation mechanisms of K. ceratoides within desert ecosystems.

Abnormal Winter Drought-Induced Transient Dieback of Korean Fir in the Montane Forests of Mt. Jirisan, South Korea

Although climate change-related concerns have long been raised regarding the sudden dieback of Korean fir (Abies koreana), the event’s etiology and subsequent ecosystem processes must be explained. Our study aims to clarify the continuity or transience of mass mortality events within the coarse woody debris (CWD) structure and, if transient, to identify the climatic conditions (1974–2021) that could be responsible for the massive dying phenomena in Korean fir populations. On average, precipitation during the non-growing season (November–April as winter) constituted 18.5% relative to the growth period; in the winter of 1999, it was 4.8% due to an abnormal drought event. The dead stems occurred evenly across all size classes. In the CWD structure, the density and biomass of the dead fir individuals peaked in decay classes II or III. The size distribution of the retained fir was inverse-J shaped across the entire altitudinal range. The abnormal winter drought event, causing root damage by soil frost and heaving, may be one of the factors that increased Korean fir mortality across the entire stem size range. Despite transient cohort senescence, the retained Korean fir individuals transmitted drought-resistant traits into the regional pool following the drought event.

Leaf nitrogen and phosphorus resorption efficiencies are related to drought resistance across woody species in a Chinese savanna.

Leaf nutrient resorption and drought resistance are crucial for the growth and survival of plants. However, our understanding of the relationships between leaf nutrient resorption and plant drought resistance is still limited. In this study, we investigated the nitrogen and phosphorus resorption efficiencies (NRE and PRE), leaf structural traits, leaf osmotic potential at full hydration (Ψosm), xylem water potential at 50% loss of xylem-specific hydraulic conductivity (P50) and seasonal minimum water potential (Ψmin) for 18 shrub and tree species in a semiarid savanna ecosystem, in Southwest China. Our results showed that NRE and PRE exhibited trade-off against drought resistance traits (Ψosm and P50) across woody species. Moreover, this relationship was modulated by leaf structural investment. Species with low structural investment (e.g., leaf mass per area, leaf dry mass content and leaf construction cost [LCC]) tend to have high NRE and PRE, while those with high LCCs show high drought resistance, showing more negative Ψosm and P50.These results indicate that species with a lower leaf structural investment may have a greater need to recycle their nutrients, thus exhibiting higher nutrient resorption efficiencies, and vice versa. In conclusion, nutrient resorption efficiency may be a crucial adaptation strategy for coexisting plants in semiarid ecosystems, highlighting the importance of understanding the complex relationships between nutrient cycling and plant survival strategies.

Suitability of the stress severity index combined with remote‐sensing data as a tool to evaluate drought resistance traits in potato

AbstractPotato is a drought susceptible crop and even short drought spells reduce tuber yields notably. In an earlier study we developed a stress severity index (SSI) based on the development stage of a genotype at the onset of drought and the soil water deficit based on soil water tension. Here, we test the suitability of the SSI combined with remotely sensed data as a screening tool to select drought‐tolerant potato genotypes. Normalized difference vegetation index (NDVI) and the photochemical reflectance index (PRI) were obtained from reflectance measurements and thermography. Temperature data from the thermography allow using the difference between leaf and air temperature (∆T) to estimate the transpirational cooling of the leaves. Via cluster analysis including SSI, tuber yield reduction under drought, NDVI, PRI and thermography, three groups were distinguished: 1. SSI &lt; 1000 with fast decreasing NDVI, PRI and ∆T, 2. SSI 1000–2000 with almost constant NDVI and ∆T and 3. SSI &gt; 2000 described by small changes of NDVI, PRI and temperature deficit. For SSI &lt; 1000, ∆T, PRI and NDVI showed to be good indicators of genotypic performance under drought. Potential strategies for drought resistance in potato detectable through remote sensing are discussed.

Drought resistance index screening and evaluation of lettuce under water deficit conditions on the basis of morphological and physiological differences.

Water is one of the important factors affecting the yield of leafy vegetables. Lettuce, as a widely planted vegetable, requires frequent irrigation due to its shallow taproot and high leaf evaporation rate. Therefore, screening drought-resistant genotypes is of great significance for lettuce production. In the present study, significant variations were observed among 13 morphological and physiological traits of 42 lettuce genotypes under normal irrigation and water-deficient conditions. Frequency analysis showed that soluble protein (SP) was evenly distributed across six intervals. Principal component analysis (PCA) was conducted to transform the 13 indexes into four independent comprehensive indicators with a cumulative contribution ratio of 94.83%. The stepwise regression analysis showed that root surface area (RSA), root volume (RV), belowground dry weight (BDW), soluble sugar (SS), SP, and leaf relative water content (RWC) could be used to evaluate and predict the drought resistance of lettuce genotypes. Furthermore, the drought resistance ranks of the genotypes were similar according to the drought resistance comprehensive evaluation value (D value), comprehensive drought resistance coefficient (CDC), and weight drought resistance coefficient (WDC). The cluster analysis enabled the division of the 42 genotypes into five drought resistance groups; among them, variety Yidali151 was divided into group I as a strongly drought-resistant variety, group II included 6 drought-resistant genotypes, group III included 16 moderately drought-resistant genotypes, group IV included 12 drought-sensitive genotypes, and group V included 7 highly drought-sensitive genotypes. Moreover, a representative lettuce variety was selected from each of the five groups to verify its water resistance ability under water deficit conditions. In the drought-resistant variety, it was observed that stomatal density, superoxide anion (O2.-wfi2) production rate, and malondialdehyde (MDA) content exhibited a low increase rate, while catalase (CAT), superoxide dismutase (SOD), and that peroxidase (POD) activity exhibited a higher increase than in the drought-sensitive variety. In summary, the identified genotypes are important because their drought-resistant traits can be used in future drought-resistant lettuce breeding programs and water-efficient cultivation.

Oryza glumaepatula: A wild relative to improve drought tolerance in cultivated rice.

Developing drought-resistant rice (Oryza sativa, L.) is essential for improving field productivity, especially in rain-fed areas affected by climate change. Wild relatives of rice are potential sources for drought-resistant traits. Therefore, we compared root growth and drought response among 22 wild Oryza species, from which Oryza glumaepatula was selected as a promising source for further exploration. A geographically diverse panel of 69 O. glumaepatula accessions was then screened for drought stress-related traits, and 6 of these accessions showed lower shoot dry weight (SDW) reduction, greater percentage of deep roots, and lower stomatal density (STO) under drought than the drought tolerant O. sativa variety, Sahbhagi dhan. Based on whole-genome resequencing of all 69 O. glumaepatula accessions and variant calling to a high-quality O. glumaepatula reference genome, we detected multiple genomic loci colocating for SDW, root dry weight at 30 to 45 cm depth, and STO in consecutive drought trials. Geo-referencing indicated that the potential drought donors originated in flood-prone locations, corroborating previous hypotheses about the coexistence of flood and drought tolerance within individual Oryza genomes. These findings present potential donor accessions, traits, and genomic loci from an AA genome wild relative of rice that, together with the recently developed reference genome, may be useful for further introgression of drought tolerance into the O. sativa backgrounds.

Genetic variation for grain nutritional profile and yield potential in sorghum and the possibility of selection for drought tolerance under irrigated conditions

BackgroundIncreasing grain nutritional value in sorghum (Sorghum bicolor) is a paramount breeding objective, as is increasing drought resistance (DR), because sorghum is grown mainly in drought-prone areas. The genetic basis of grain nutritional traits remains largely unknown. Marker-assisted selection using significant loci identified through genome-wide association study (GWAS) shows potential for selecting desirable traits in crops. This study assessed natural variation available in sorghum accessions from around the globe to identify novel genes or genomic regions with potential for improving grain nutritional value, and to study associations between DR traits and grain weight and nutritional composition.ResultsWe dissected the genetic architecture of grain nutritional composition, protein content, thousand-kernel weight (TKW), and plant height (PH) in sorghum through GWAS of 163 unique African and Asian accessions under irrigated and post-flowering drought conditions. Several QTLs were detected. Some were significantly associated with DR, TKW, PH, protein, and Zn, Mn, and Ca contents. Genomic regions on chromosomes 1, 2, 4, 8, 9, and 10 were associated with TKW, nutritional, and DR traits; colocalization patterns of these markers indicate potential for simultaneous improvement of these traits. In African accessions, markers associated with TKW were mapped to six regions also associated with protein, Zn, Ca, Mn, Na, and DR, suggesting the potential for simultaneous selection for higher grain nutrition and TKW. Our results indicate that it may be possible to select for increased DR on the basis of grain nutrition and weight potential.ConclusionsThis study provides a valuable resource for selecting landraces for use in plant breeding programs and for identifying loci that may contribute to grain nutrition and weight with the hope of producing cultivars that combine improved yield traits, nutrition, and DR.

Unique drought resistance strategies occur among monkeyflower populations spanning an aridity gradient.

Annual plants often exhibit drought-escape and avoidance strategies to cope with limited water availability. Determining the extent of variation and factors underlying the evolution of divergent strategies is necessary for determining population responses to more frequent and severe droughts. We leveraged five Mimulus guttatus populations collected across an aridity gradient within manipulative drought and quantitative genetics experiments to examine constitutive and terminal-drought induced responses in drought resistance traits. Populations varied considerably in drought-escape- and drought-avoidance-associated traits. The most mesic population demonstrated a unique resource conservative strategy. Xeric populations exhibited extreme plasticity when exposed to terminal drought that included flowering earlier at shorter heights, increasing water-use efficiency, and shifting C:N ratios. However, plasticity responses also differed between populations, with two populations slowing growth rates and flowering at earlier nodes and another population increasing growth rate. While nearly all traits were heritable, phenotypic correlations differed substantially between treatments and often, populations. Our results suggest drought resistance strategies of populations may be finely adapted to local patterns of water availability. Substantial plastic responses suggest that xeric populations can already acclimate to drought through plasticity, but populations not frequently exposed to drought may be more vulnerable.

Genetic dissection of drought resistance for trait improvement in crops

Reliance on agriculture for food security is a constant in all modern societies. Global climate change and population growth have put immense pressure on sustainable agriculture, exacerbating the effects of environmental stresses. Drought is one of the most pressing abiotic stresses that farmers face, presenting an annual threat to crop growth and yield. Crops have evolved extensive morphological, physiological, and molecular mechanisms to combat drought stress. Drought resistance is a polygenic trait, controlled by a complex genetic network and an array of genes working together to ensure plant survival. Many studies have aimed at dissecting the genetic mechanisms underlying drought resistance. Recent studies using linkage and association mapping have made progress in identifying genetic variations that affect drought-resistance traits. These loci may potentially be engineered by genetic transformation and genome editing aimed at developing new, stress-resistant crop cultivars. Here we summarize recent progress in elucidating the genetic basis of crop drought resistance. Molecular-breeding technologies such as marker-assisted selection, genome selection, gene transformation, and genome editing are currently employed to develop drought-resistant germplasm in a variety of crops. Recent advances in basic research and crop biotechnology covered in this review will facilitate delivery of drought-resistant crops with unprecedented efficiency.

Screening and evaluation of drought resistance traits of winter wheat in the North China Plain.

Drought-resistant varieties are an important way to address the conflict between wheat's high water demand and the scarcity of water resources in the North China Plain (NCP). Drought stress impacts many morphological and physiological indicators in winter wheat. To increase the effectiveness of breeding drought-tolerant varieties, choosing indices that can accurately indicate a variety's drought resistance is advantageous. From 2019 to 2021, 16 representative winter wheat cultivars were cultivated in the field, and 24 traits, including morphological, photosynthetic, physiological, canopy, and yield component traits, were measured to evaluate the drought tolerance of the cultivars. Principal component analysis (PCA) was used to transform 24 conventional traits into 7 independent, comprehensive indices, and 10 drought tolerance indicators were screened out by regression analysis. The 10 drought tolerance indicators were plant height (PH), spike number (SN), spikelet per spike(SP), canopy temperature (CT), leaf water content (LWC), photosynthetic rate (A), intercellular CO2 concentration (Ci), peroxidase activity (POD), malondialdehyde content (MDA), and abscisic acid (ABA). In addition, through membership function and cluster analysis, 16 wheat varieties were divided into 3 categories: drought-resistant, drought weak sensitive, and drought-sensitive. JM418, HM19,SM22, H4399, HG35, and GY2018 exhibited excellent drought tolerance and,therefore, can be used as ideal references to study the drought tolerance mechanism in wheat and breeding drought-tolerant wheatcultivars.

Comparison of Various Drought Resistance Traits in Soybean (Glycine max L.) Based on Image Analysis for Precision Agriculture.

Drought is being annually exacerbated by recent global warming, leading to crucial damage of crop growth and final yields. Soybean, one of the most consumed crops worldwide, has also been affected in the process. The development of a resistant cultivar is required to solve this problem, which is considered the most efficient method for crop producers. To accelerate breeding cycles, genetic engineering and high-throughput phenotyping technologies have replaced conventional breeding methods. However, the current novel phenotyping method still needs to be optimized by species and varieties. Therefore, we aimed to assess the most appropriate and effective phenotypes for evaluating drought stress by applying a high-throughput image-based method on the nested association mapping (NAM) population of soybeans. The acquired image-based traits from the phenotyping platform were divided into three large categories-area, boundary, and color-and demonstrated an aspect for each characteristic. Analysis on categorized traits interpreted stress responses in morphological and physiological changes. The evaluation of drought stress regardless of varieties was possible by combining various image-based traits. We might suggest that a combination of image-based traits obtained using computer vision can be more efficient than using only one trait for the precision agriculture.

Genome-wide association study presents insights into the genetic architecture of drought tolerance in maize seedlings under field water-deficit conditions.

Drought stress is one of the most serious abiotic stresses leading to crop yield reduction. Due to the wide range of planting areas, the production of maize is particularly affected by global drought stress. The cultivation of drought-resistant maize varieties can achieve relatively high, stable yield in arid and semi-arid zones and in the erratic rainfall or occasional drought areas. Therefore, to a great degree, the adverse impact of drought on maize yield can be mitigated by developing drought-resistant or -tolerant varieties. However, the efficacy of traditional breeding solely relying on phenotypic selection is not adequate for the need of maize drought-resistant varieties. Revealing the genetic basis enables to guide the genetic improvement of maize drought tolerance. We utilized a maize association panel of 379 inbred lines with tropical, subtropical and temperate backgrounds to analyze the genetic structure of maize drought tolerance at seedling stage. We obtained the high quality 7837 SNPs from DArT's and 91,003 SNPs from GBS, and a resultant combination of 97,862 SNPs of GBS with DArT's. The maize population presented the lower her-itabilities of the seedling emergence rate (ER), seedling plant height (SPH) and grain yield (GY) under field drought conditions. GWAS analysis by MLM and BLINK models with the phenotypic data and 97862 SNPs revealed 15 variants that were significantly independent related to drought-resistant traits at the seedling stage above the threshold of P < 1.02 × 10-5. We found 15 candidate genes for drought resistance at the seedling stage that may involve in (1) metabolism (Zm00001d012176, Zm00001d012101, Zm00001d009488); (2) programmed cell death (Zm00001d053952); (3) transcriptional regulation (Zm00001d037771, Zm00001d053859, Zm00001d031861, Zm00001d038930, Zm00001d049400, Zm00001d045128 and Zm00001d043036); (4) autophagy (Zm00001d028417); and (5) cell growth and development (Zm00001d017495). The most of them in B73 maize line were shown to change the expression pattern in response to drought stress. These results provide useful information for understanding the genetic basis of drought stress tolerance of maize at seedling stage.

Plant water‐use strategies predict restoration success across degraded drylands

Abstract Plant strategies for coping with water limitation are likely to mediate restoration outcomes in degraded dryland ecosystems. Trade‐offs in traits related to water acquisition and use can intensify in more arid environments, making their effects on dryland restoration success even more salient. However, isolating the effects of drought responses from those of other environmental factors, as well as identifying the specific drought resistance traits that influence restoration success, can be difficult. In the present study, we couple a controlled dry‐down experiment with a cross‐site restoration field trial of out‐planted seedlings (RestoreNet) using a suite of dryland herbaceous plant species from the same seed sources. We quantified interspecific variation in physiological responses to drought, specifically reductions in stomatal conductance (gs) and stem water potential (SWP), by comparing well‐watered control plants to those experiencing decreasing soil moisture. Drought responses of SWP and gs varied independently among species, but both were related to survival in the cross‐site restoration field trial when effect sizes were aggregated across all sites. Responses were consistent with acquisitive water‐use strategies resulting in greater success, where species with greater declines in SWP or weaker declines in gs under drought had greater survival. The correlation between SWP drought response and survival also intensified in sites with lower accumulated precipitation following restoration. Differences among functional groups revealed two different paths to restoration success: forbs that maintain high gs and narrow safety margins to maximize exploitation of moisture pulses before going into drought dormancy, or C4 grasses that maintain efficient water uptake in drying soils while risking cavitation. C3 grass species varied between these two strategies. Synthesis and applications. Taken together, the results of this study and others conducted at RestoreNet sites indicate that while a diversity of physiological responses to drought may exist in dryland plant communities, successfully restoring herbaceous species through out‐planting in degraded conditions is likely to be achieved with species that maximize water uptake via one of two strategies, with tolerance of low SWP being particularly important in the most arid settings.

How Changes in ABA Accumulation and Signaling Influence Tomato Drought Responses and Reproductive Development

Water deficit conditions trigger the production of a chemical signal, the phytohormone abscisic acid (ABA), which coordinates multiple responses at different temporal and spatial scales. Despite the complexity of natural drought conditions, the modulation of ABA signaling could be harnessed to ameliorate the drought performances of crops in the face of increasingly challenging climate conditions. Based on recent studies, increasing ABA sensitivity can lead to genotypes with improved drought resistance traits, with sustained biomass production in water-limiting environments and little or no costs with respect to biomass production under optimal conditions. However, variations in ABA production and sensitivity lead to changes in various aspects of reproductive development, including flowering time. Here we provide an updated summary of the literature on ABA-related genes in tomato and discuss how their manipulation can impact water-deficit-related responses and/or other developmental traits. We suggest that a better understanding of specific ABA components’ function or their expression may offer novel tools to specifically engineer drought resistance without affecting developmental traits.